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Old 10-03-2007, 09:29 AM
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Ballast resistor

I have a mid 70's 350 Chev motor in my 32 sedan. It has a Mallory electronic distributor that is pointless and an external coil. I currently have a ballast resistor installed but was told I do not need it with an electronic distributor. Is this correct?
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Old 10-03-2007, 10:15 AM
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the ballast resistor is there to make 12vdc work @ 6vdc. If the product you are using is ment to use 12vdc I would recommend you remove it, cause you are suppling the unit with 1/2 the voltage it was designed to work with. Points would arc as they opened an closed, a capacitor was installed to eliminate this, it was located next to the points and was designed to work at 6vdc, along came the 12vdc system and therefore the ballast resistor.
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Old 10-04-2007, 04:33 PM
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with mallory yes

I would keep it. Mallory recommends that you do. If you use a hyfire box you don't need it but I would still keep it. I have a unilite procoil and hyfire box and still use it. It will help with spikes. I have mi resistor inside under the dash out of sight.
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Old 10-07-2007, 11:22 PM
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Ballast Resistor?

The whole reason that a "ballast resistor" is installed in a "points" type ignition system is to let the coil recieve 12 volts during cranking. Once the engine is "fired", the voltage is reduced to about 9 volts to make the load on the coil lighter. Your system is designed to run on 12 volts from start-up to run and does not need a ballast resistor to reduce the voltage after start-up and is designed to run on 12 volts all of the time! Your's, Westfalia Guy.
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Old 10-10-2007, 10:29 PM
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Quote:
Originally Posted by westfaliaguy
The whole reason that a "ballast resistor" is installed in a "points" type ignition system is to let the coil recieve 12 volts during cranking. Once the engine is "fired", the voltage is reduced to about 9 volts to make the load on the coil lighter. Your system is designed to run on 12 volts from start-up to run and does not need a ballast resistor to reduce the voltage after start-up and is designed to run on 12 volts all of the time! Your's, Westfalia Guy.
Found this in the Mallory online catalog along with an illustration of the ballast (not shown here). This indicates to me that if Timkins ( or anyone else) are using a mallory Unilite pointless converson or distributor, they need a ballast.

Ballast Resistor
Heavy duty porcelain resistor with threaded terminal
connectors is rated at 200 watts and 0.75 – 1.5 ohms.
Variable resistance values improve cold weather starting.
Direct replacement for old Mallory Part Numbers 25750-38
and 28127. Designed for use with E-spark, MBI and UniLite
distributors (Ex. w/HyFire CD Ingitions)
Ballast Resistor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 700

Last edited by artsman; 10-10-2007 at 10:36 PM. Reason: additional comment
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Old 10-10-2007, 10:47 PM
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Quote:
Originally Posted by tomthecomic
I would keep it. Mallory recommends that you do. If you use a hyfire box you don't need it but I would still keep it. I have a unilite procoil and hyfire box and still use it. It will help with spikes. I have mi resistor inside under the dash out of sight.
Checkout my reply to westfallaguy. And this paste from the Mallory online cataloge...Doug

Ballast Resistor
Heavy duty porcelain resistor with threaded terminal
connectors is rated at 200 watts and 0.75 – 1.5 ohms.
Variable resistance values improve cold weather starting.
Direct replacement for old Mallory Part Numbers 25750-38
and 28127. Designed for use with E-spark, MBI and UniLite
distributors (Ex. w/HyFire CD Ingitions)
Ballast Resistor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 700
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Old 10-11-2007, 05:10 AM
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timkens,

since you gave no clue as to which model or type Mallory you have....look up your dist wiring instructions on this link:

http://www.malloryperformance.com/In...aspx?BrandID=6

if it is a unilite...you do need a ballast resistor or you can/will blow the photo eye sensor bulb (and need a tow truck to get home)

yes, the ballast resistor knocks down the voltage to 6-9V at idle....when only the batt is supplying V....once the alt kicks in it over powers the resistor....V goes up to about 11 and 8 amps (at roughly 2,000rpms)....which is the practical max for the photo sensor
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Old 10-12-2007, 05:33 PM
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The two mallory unilites that I have are on Chevy 327's. The technical division at Summit specified a 1.5 ohm flamethrower coil and removing the ballast resistor. What is going on with this ? Now I'm lost, here, clutching the fire extinguisher.
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Old 10-12-2007, 05:46 PM
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seven up

early Chevy's have a 1.5 ohm (ballast) resistor "wire" in the ign harness (usually bright pink with really soft insulation and cloth covered) that feeds to the dist

"if" you have that wire you don't want another 1.5ohm ballast resistor on the dist feed wire....volts at idle would be down to like 4 max

yes, a 1.5 ohm coil is normal/typical to use with a unilite so there is 8 amps max (and/or a ballast resistor and/or a resistor wire to end up at 1.5ohms plus depending on the coil ohms)

Last edited by red65mustang; 10-13-2007 at 08:50 AM.
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Old 10-12-2007, 11:06 PM
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timkins,

Well I dug out the unilite paperwork. The function of the ballast resistor in this application is to reduce current flow to the electronic module, not voltage. The recommended ballast resistor mallory pn 700 is a variable resistance ballast 0.7 ohms to 1.5. Also, if a coil with the proper resistance is used (with a mallory part number suggested), the use of a ballast resistor is not necessary. And no solid core spark plug wires.

So summit tech gave me the proper recommendation and sold the proper parts. The flamethrower was a little less than the equivalent mallory.

I'm glad I didn't call and tell them they were full of s**t !

A vacuum advance distributor may be different. No pink wire on mine. I think i wrote ballast resitor.

Nite
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Old 10-13-2007, 07:26 AM
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Distributor

Sorry it took so long to get back. The distributor is a Mallory UniLite 47 series. The part number is 4748201A. I currently have the vacuum port for the distributor plugged as I was running about 57 deg advance when it was hooked up to the vacuum. The question about a ballast resistor was generated at a cruise night and somebody said it was not required with a Mallory distributor.
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Old 10-13-2007, 08:44 AM
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hopefully to clarify?

seven up,
yes, it is current=amps that need to be restricted with ohms to about 8 amps max due to the limited heat disappation capability of the module....
and yes voltage resistance (to about 11V) is needed to protect the 12V to SS 5V step down conversion which includes the protecting the bulb
(thats why Mallory sells a "spike protector" kit for the unilite)

the Mallory coil 29219 which does not require a ballast resistor is 1.4ohms primary resistance....12V/1.4=8.5 amps

the other coil recommended, 29216 is a typical "performance" coil of .7 ohms primary resistance for more amps in the spark....12V/.7=17amps...way to many amps and to much heat...you do need atleast a additional .7ohms resistor

bottem line, for a unilite you have to know your coils specific internal primary resistance so that you do end up at 1.5 ohms and 8 amps....
if you do use a .7ohms coil and a 1.5ohm resistor=about 5amps=never fail(?)....that's still alot better spark than points at 3amps typical

footnote: same applies to pertronix, you want to be at the 8 amps practical max for strongest spark "kernel" for best "burn"
(I use a .6ohm Jacobs coil with a .8ohm MSD ballast resistor with my pertronix)

apology: I had to edit my previous post, so it makes more sense

ps: practical minimum voltage to get a module to work is about 8V...so a weak batt and hot starter pulling down the V can cause a no spark

pps: ALL the instruction sheets are on the link I posted

Last edited by red65mustang; 10-13-2007 at 09:00 AM.
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Old 10-13-2007, 09:06 AM
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timken,
measure your coil's primary resistance

see attached left side diagram
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